JP4766966B2 - Light emitting element - Google Patents

Description

The present invention relates to a light emitting device in which a plurality of gallium nitride compound semiconductors (In _x Al _y Ga _1-xy N; 0 ≦ x, y ≦ 1, x + y ≦ 1) are stacked.

The gallium nitride compound semiconductor (In _x Al _y Ga _1-xy N; 0 ≦ x, y ≦ 1, x + y ≦ 1) is made of AlGaN, InGaN, InGaAlN or the like which is a mixed crystal of AlN, InN or the like. By selecting the composition, light emission from the visible region to the ultraviolet region is possible, and it has been studied as a light emitting device material such as a semiconductor light emitting diode (LED) and a semiconductor laser, and has been partially put into practical use. Yes. In addition, it has been studied as a semiconductor material such as a field effect transistor, and is expected as a high-output high-frequency device, and is being developed.

  FIG. 1 shows a cross-sectional view of a conventional light emitting device. The light emitting element uses, for example, a substrate 10 such as sapphire as a substrate, and an n-type gallium nitride compound semiconductor layer (hereinafter also referred to as n-type layer) 12 and a light emitting layer (active layer) via a buffer layer 11 on the substrate 10. ) 13, a p-type gallium nitride compound semiconductor layer (hereinafter also referred to as a p-type layer) 14 is formed, a part of the p-type layer 14 is etched away to form the n-type electrode 15, and the n-type layer 12 is removed. Some are exposed. The p-type electrode 16 is formed by forming a transparent electrode 16 on one surface of the p-type layer 14 in order to extract light emitted from the light-emitting layer 13 to the p-type layer 14 side, and performing wire bonding on a part of the transparent electrode 16. In general, a structure in which a pad electrode is formed is provided.

  In the LED having such a configuration, the light emitted from the light emitting layer 13 is reflected at the interface with the substrate 10 due to the difference in refractive index between the substrate 10 such as sapphire and the gallium nitride compound semiconductor layer or air, and the buffer layer. The light that has returned to the inside of the semiconductor layer composed of the n-type layer 12, the light-emitting layer 13, and the p-type layer 14 cannot be efficiently extracted to the outside due to absorption in the semiconductor layer during multiple reflection. That is, there is a problem that the external quantum efficiency cannot be increased.

  Therefore, for example, Patent Documents 1 and 2 disclose that the extraction of light to the outside is improved by processing the surface of the semiconductor layer serving as the light extraction surface into an uneven shape.

Further, when extracting light from the substrate side, there is a method of removing the substrate itself in order to eliminate the influence of the absorption of the substrate itself and the reflection at the interface between the substrate and the semiconductor layer and increase the light extraction efficiency. 3 and Non-Patent Document 4.
JP 2000-196152 A JP 2003-218383 A JP-T-2004-508720 Jpn. J. Appl. Phys. Vol. 41 (2002) pp.L1434-1436

  However, in the method of making irregularities on the surface of the semiconductor layer that becomes the light extraction surface as in Patent Documents 1 and 2, the effect of buffering the refractive index cannot be obtained unless the irregularities are made to the nano-order level. It is difficult to control, and when the uneven shape is formed by dry etching such as reactive ion etching (RIE), the semiconductor layer may be damaged at that time.

  In order to remove the substrate, the light emitting element is once attached to a support material called a carrier, and the interface between the semiconductor layer and the semiconductor layer such as sapphire used for the growth of the semiconductor layer is melted by a laser or the like, for example. Is used, but a complicated process such as attachment to a support material and substrate peeling is required, resulting in poor manufacturing yield. In the laser lift-off method, damage to the semiconductor layer due to laser irradiation may occur.

  Furthermore, due to the difference in lattice constant and thermal expansion between the substrate and the gallium nitride compound semiconductor layer, the strain introduced into the semiconductor layer during the stacking is released when the substrate is peeled off, thereby There is a problem that cracks, cracks, etc. occur.

  The present invention has been made in view of such problems, and it is possible to extract light emitted from the light emitting layer without performing complicated steps such as a concave / convex structure forming step by dry etching on the semiconductor layer and a substrate removing step. In other words, the external quantum efficiency of a light emitting device using a gallium nitride compound semiconductor is improved.

In the light emitting device of the present invention, a semiconductor layer including an n-type gallium nitride compound semiconductor layer, a p-type gallium nitride compound semiconductor layer, and a light emitting layer made of a gallium nitride compound semiconductor is formed on an upper surface of a substrate made of sapphire. The n-type electrode connected to the n-type gallium nitride compound semiconductor layer and the p-type electrode connected to the p-type gallium nitride compound semiconductor layer are formed in the same main surface direction of the semiconductor layer. in the flip-chip light emitting device structure light emitted from the light emitting layer is taken out from the substrate side, the substrate is a through hole that reaches the semiconductor layer through the upper and lower surfaces formed with a plurality, the through hole the diameter D _h, the refractive index of the semiconductor layer n ₁ and the refractive index of the through-hole and n _2, the distance from the light-emitting layer to the substrate is taken as D _s, D _h 2 × _{D s} × tanθ _{r (however, θ r = arcsin (n 1} / n 2)) , characterized in der Rukoto.

  In the light-emitting element of the present invention, preferably, the semiconductor layer is roughened only in a portion facing the through hole in a surface in contact with the upper surface of the substrate.

  In the light emitting device of the present invention, preferably, the through hole is filled with a translucent member having a refractive index between a refractive index of air and a refractive index of the gallium nitride compound semiconductor. And

Further, preferably the light-emitting device of the present invention, the through hole is characterized in that reflective member for reflecting light emitted from the light emitting layer on the side surface is provided.

The light emitting device of the present invention is preferably characterized in that the opening ratio of the through-hole, which is a ratio of the area of the upper and lower surfaces of the substrate, is 50% or more and 95% or less .

In the light emitting device of the present invention, it is preferable that the diameter of the through hole gradually decreases toward the interface between the substrate and the semiconductor layer .

In the light emitting device of the present invention, a semiconductor layer including an n-type gallium nitride compound semiconductor layer, a p-type gallium nitride compound semiconductor layer, and a light emitting layer made of a gallium nitride compound semiconductor is formed on an upper surface of a substrate made of sapphire. The n-type electrode connected to the n-type gallium nitride compound semiconductor layer and the p-type electrode connected to the p-type gallium nitride compound semiconductor layer are formed in the same main surface direction of the semiconductor layer. In the light emitting element having a flip chip structure in which light emitted from the light emitting layer is extracted from the substrate side, the substrate has a plurality of through holes that penetrate the upper and lower surfaces and reach the semiconductor layer, and the diameter of the through hole D _h is the refractive index of the semiconductor layer n ₁ and the refractive index of the through-hole and n _2, the distance from the light-emitting layer to the substrate is taken as _{D s, D h ≧ 2 ×} D × tan .theta _{r (however, θ r = arcsin (n 1} / n 2)) from Der Rukoto, but generally light emitted from the light emitting layer is often component reflected at the interface between the substrate and the semiconductor layer, the present invention When the through hole is formed in the substrate as described above, light is emitted to the outside through the through hole. In addition, since light does not propagate through the substrate, light absorption in the substrate can be suppressed as much as possible, and light emitted inside the semiconductor layer can be efficiently extracted to the outside. The light emitting device of the present invention is particularly suitable for extracting light from the substrate side such as a flip chip structure.

  In the light emitting device of the present invention, preferably, the semiconductor layer is roughened only in a portion facing the through hole in a surface in contact with the upper surface of the substrate. The step-like change in refractive index at the interface with the space inside the through hole can be alleviated, and as a result, light can be efficiently extracted from the semiconductor layer to the space inside the through hole. In addition, since the semiconductor layer is not roughened except for the part facing the through hole in the surface in contact with the upper surface of the substrate, the adhesion and bonding properties between the substrate and the semiconductor layer are improved. Furthermore, since only the portion facing the through hole is roughened, damage due to the roughening can also be suppressed.

  In the light emitting device of the present invention, preferably, the through hole is filled with a translucent member having a refractive index between the refractive index of air and the refractive index of the gallium nitride compound semiconductor. The critical angle when light is emitted from the through hole to the inner space of the through hole is increased, and light can be extracted efficiently. Furthermore, since the through hole is filled with a light-transmitting member, a reduction in the strength of the substrate due to the formation of the through hole can be suppressed, and the thickness of the substrate can be reduced.

The light emitting element is preferably of the present invention, the through-holes, since the reflective member for reflecting light emitted by the light emitting layer on the side surface is provided, in which light is extracted to the substrate side from the semi-conductor layer The light can be efficiently reflected by the side surface of the through hole, and the light extraction efficiency to the substrate side can be increased.

In the light emitting device of the present invention, preferably, the opening of the through hole has an aperture ratio that is a ratio of the area of the upper and lower surfaces of the substrate of 50% to 95% . The semiconductor layer can be supported by the substrate while improving the extraction efficiency .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 2 shows the configuration of the light emitting device according to the first embodiment of the present invention, in which a gallium nitride compound semiconductor 100 is formed on the substrate 10 via the buffer layer 11 by the MOCVD method. In the light emitting device shown in FIG. 2, a first conductivity type (for example, n-type) gallium nitride compound semiconductor layer (hereinafter also referred to as an n-type layer) 12 is formed on a substrate 10 via a buffer layer 11, and then continues on that. A light emitting layer 13 is formed, and finally a second conductivity type (for example, p-type) gallium nitride compound semiconductor layer (hereinafter also referred to as a p-type layer) 14 is laminated.

  Furthermore, in order to expose a part of the n-type layer 12, a part of the p-type layer 14 and the light-emitting layer 13 is removed, and the n-type electrode 15 is in ohmic contact with the n-type on the exposed surface of the n-type layer 12. And a p-type electrode 16 in ohmic contact with the p-type layer 14 is formed on the surface of the p-type layer 14.

  In the present embodiment, the first conductivity type is n-type and the second conductivity type is p-type, but the first conductivity type may be p-type and the second conductivity type may be n-type.

In the present invention, the substrate 10 is preferably a diboride single crystal represented by the chemical formula XB ₂ (where X includes at least one of Ti and Zr). More preferably, zirconium diboride (ZrB ₂ ) can be used, but other impurities may be included to such an extent that the crystallinity and lattice constant of ZrB ₂ do not change greatly.

Examples of the material of the substrate 10 include sapphire (Al ₂ O ₃ ), silicon carbide (SiC), gallium nitride (GaN), silicon (Si), and zinc oxide (ZnO). The material is not particularly limited as long as the material can grow the compound semiconductor layer. However, the effect of forming the through hole of the present invention becomes more remarkable as the substrate 10 is made of a material that absorbs light emitted from the light emitting layer 13.

  The buffer layer 11 is not necessarily formed when the lattice constant and the thermal expansion coefficient of the gallium nitride compound semiconductor 100 and the substrate 10 are close, but gallium nitride (GaN), aluminum nitride (AlN), or a mixture thereof. Crystalline gallium aluminum nitride (AlGaN) can be used.

  After the buffer layer 11 is formed, the temperature is raised and the n-type layer 12 is subsequently formed. In FIG. 2, a GaN layer is grown as the n-type layer 12, but a mixed crystal composition of AlN, indium nitride (InN), such as AlGaN, InGaN, or the like may be used. Examples of the growth method include a molecular beam epitaxy (MBE) method, a hydride vapor phase epitaxy (HVPE) method, and a pulsed laser deposition (PLD) method in addition to the MOCVD method.

  The formation temperatures of the buffer layer 11 and the gallium nitride compound semiconductor 100 are 400 ° C. to 800 ° C. and 800 ° C. to 1100 ° C., respectively.

  The n-type layer 12 is doped with Si or the like as an impurity element, but an AlGaN layer or an InGaN layer may be formed on the n-type layer 12 or may not be a single layer. Is partially exposed, and the n-type electrode 15 is required to be formed on the surface thereof.

The light emitting layer 13 has a multilayer quantum well structure (MQW) in which a quantum well structure composed of a barrier layer having a wide forbidden band and a well layer having a narrow forbidden band is regularly stacked a plurality of times (not shown). ). The structure is made of InN, GaN, AlN, or a mixed crystal thereof, and is appropriately combined depending on the emission wavelength. For example, a combination using In _x Ga _1-x N as the well layer and In _y Ga _1-y N (where x> y ≧ 0) as the barrier layer is possible.

  The formation temperature of the light emitting layer (active layer) 13 is 700 ° C. to 900 ° C. as in the cap layer 13 although it depends on the composition of indium (In). In order to eliminate the diffusion of boron (B) from the substrate 10, a lower one of 700 ° C. to 800 ° C. is preferable.

  Moreover, the thickness of the barrier layer is 5 to 15 nm, the thickness of the well layer is 3 to 10 nm, and the number of repetitions of the quantum well structure is 3 to 5 layers, but is not limited thereto.

  Furthermore, the p-type layer 14 formed on the light emitting layer 13 is composed of a plurality of layers such as an AlGaN layer and a GaN layer (not shown). As a p-type impurity element contained in the p-type layer 14, magnesium (Mg), zinc (Zn), or the like is added.

Further, the n-type electrode 15 formed on a part of the exposed n-type layer 12 is a layered material made of a material capable of making good ohmic contact with the n-type layer 12. Examples of such materials include thinly formed aluminum (Al), titanium (Ti), nickel (Ni), chromium (Cr), indium (In), tin (Sn), molybdenum (Mo), silver (Ag). ), Gold (Au), niobium (Nb), tantalum (Ta), vanadium (V), platinum (Pt), or the like, or tin oxide (SnO ₂ ), indium oxide (In ₂ O ₃ ), indium tin oxide Examples thereof include thin films such as (ITO) and zinc oxide (ZnO). Further, a plurality of the above thin films or a compound may be used. Preferably, a layer in which a Ti layer, an Al layer, a Ni layer, and an Au layer are sequentially stacked is used.

Further, the p-type electrode 16 formed on the p-type layer 14 is made of a material that can make a good ohmic contact with the p-type layer 14. Examples of such materials include thinly formed aluminum (Al), titanium (Ti), nickel (Ni), chromium (Cr), indium (In), tin (Sn), molybdenum (Mo), silver (Ag). ), Gold (Au), niobium (Nb), tantalum (Ta), vanadium (V), platinum (Pt), rhodium (Rh), palladium (Pd), etc., or tin oxide (SnO ₂ ), indium oxide Examples thereof include thin films such as (In ₂ O ₃ ), indium tin oxide (ITO), and zinc oxide (ZnO). Further, a plurality of the above thin films or a compound may be used.

  Furthermore, the material of the p-type electrode 16 can be appropriately selected from a reflective material and a transmissive material depending on the direction in which light generated in the light emitting layer 13 of the light emitting element is extracted. For example, when light is extracted to the p-type layer 14 side, a transparent electrode formed by sequentially laminating a Ni thin film and an Au thin film is used as the electrode 16, and when light is extracted to the substrate side, a reflective material, for example, A thin film made of silver (Ag), aluminum (Al), rhodium (Rh), palladium (Pd) can be suitably used.

  In the first embodiment, a plurality of through holes 17 opened in the substrate 10 are formed so as to reach the buffer layer 11. As shown in FIGS. 3A and 3B, the through-hole 17 may have a constant diameter across the upper and lower surfaces of the substrate 10 in the longitudinal cross-sectional shape, and the diameter may change. It may be. For example, a configuration in which the diameter gradually decreases from the lower surface of the substrate 10 toward the interface between the substrate 10 and the semiconductor layer, and conversely, a configuration in which the diameter increases may be employed. The through hole 17 may also penetrate the buffer layer 11 and reach the n-type layer 12. The number of through holes 17 is one or more.

  In addition, since a plurality of through holes 17 are formed, the above effect becomes more remarkable, and light can be extracted efficiently. Further, unlike the case where all of the substrate 10 is removed from the semiconductor layer, no support material is required, and the substrate 10 has the through holes 17, but other than the through holes 17 are partially left. Therefore, the semiconductor layer can be supported. Therefore, a complicated process is not required.

The diameter of each through hole 17 is the distance from the light emitting layer 13 to the interface between the substrate 10 and the buffer layer 11, the refractive index (n ₁ ) of the semiconductor layer, and the refractive index of the substance in the through hole 17 ( the n ₂₎ and the critical angle theta _r = arcsin determined by _(n 1 / _{n 2),} it is possible to determine the effective minimum diameter. That is, when the diameter of the through hole 17 is D _h (μm) and the distance from the light emitting layer 13 to the interface between the substrate 10 and the buffer layer 11 is D _s , the smallest through hole 17 that can efficiently extract light. Can be determined by D _h = 2 · D _s · tan θ _r .

  Since the refractive index of a gallium nitride compound semiconductor is 2.5 and air is 1, the critical angle θr is about 23 ° in the present embodiment. Therefore, when the distance from the light emitting layer 13 to the interface 11 between the substrate 10 and the buffer layer is 2 μm, the minimum diameter of the through hole 17 can be determined to be about 1.7 μm. If the diameter of the through hole 17 is equal to or larger than the minimum diameter, light can be effectively extracted through the through hole 17.

  Further, the ratio of the one or more through-holes 17 to the area of the upper and lower surfaces of the substrate 10, that is, the aperture ratio is preferably 50% or more, and preferably 95% or less. When the aperture ratio is less than 50%, the improvement of light extraction efficiency is not so remarkable, and the influence of the absorption of the substrate 10 is large. Further, when the aperture ratio is larger than 95%, it becomes difficult to support the semiconductor layer, and the substrate 10 is cracked or broken. The aperture ratio is preferably as large as possible, but it is preferable to select it appropriately in consideration of the support properties of the substrate 10 material.

  Further, the sizes of the openings on the upper and lower surfaces of the substrate 10 of the through holes 17 do not have to be constant, and may be configured by a combination of openings having different sizes.

  Moreover, when forming the several through-hole 17, the arrangement | sequence may be arranged along a fixed rule, and may be arranged at random.

  An example of an embodiment of the various opening shapes of the through hole 17 as described above is shown in the plan views (plan views on the upper and lower surfaces of the substrate 10) of FIGS. The shape of the through-hole 17 should just satisfy | fill the diameter and aperture ratio of said through-hole 17, and the same effect can be acquired. Here, the diameter of the through-hole 17 indicates the shortest distance of the opening. For example, if the circular shape is as shown in FIGS. 4 (d) and 4 (e), the diameter is represented as shown in FIGS. 4 (a) to 4 (c). In a rectangular shape, the length of the shortest side is shown, and in the polygon as shown in FIG. 4 (f), the distance between opposing sides is shown.

Such through-holes 17, for example, if the substrate 10 is made of ZrB _2, it can be formed by wet etching using hydrofluoric-nitric acid. The etching time can be shortened by thinning the substrate 10 by mechanical polishing before wet etching.

  Preferably, in the light emitting device of the present invention, the semiconductor layer is roughened only in a portion facing the through hole 17 in the surface in contact with the upper surface of the substrate 10. In this case, the semiconductor layer is formed on the substrate 10. Thus, wet etching with hydrofluoric acid is performed on the substrate 10 to form the through-hole 17 and to roughen only a portion of the surface of the semiconductor layer that faces the upper surface of the substrate 10 that faces the through-hole 17. Thereby, in the roughened part, the step-like change in the refractive index at the interface between the semiconductor layer and the space inside the through hole 17 can be alleviated. As a result, the through hole 17 is formed from the inside of the semiconductor layer. Light can be efficiently extracted into the inner space. In addition, since the semiconductor layer is not roughened except for the portion facing the through hole 17 in the surface in contact with the upper surface of the substrate 10, the adhesion and bonding properties between the substrate 10 and the semiconductor layer are improved. Further, since only the portion facing the through hole 17 is roughened, damage due to the roughening can also be suppressed.

  Of the surface in contact with the upper surface of the substrate 10 in the semiconductor layer having the above effect, the arithmetic average roughness of the roughened portion facing the through hole 17 is preferably about 100 nm to 1 μm, and is roughened. The aspect ratio (height / roughness) of the height and roughness (roughness period) of the unevenness of the part is preferably 1 to 5.

  Furthermore, the configuration of the second embodiment of the present invention is shown in FIG. In the present embodiment, as in the first embodiment, the gallium nitride compound semiconductor 100 is formed on the substrate 10 via the buffer layer 11 by the MOCVD method. And in this Embodiment, the translucent member 18 which has the refractive index between air and the gallium nitride type compound semiconductor is filled in the through-hole 17 opened in the board | substrate 10. FIG. As such a translucent member 18, a resin material is suitable, and in particular, a silicone-based resin is preferred in terms of durability and light transmissibility. The refractive index of a gallium nitride compound semiconductor is about 2.5, the refractive index of air is 1, and the refractive index of such a resin material is about 1.5, which is critical when light is extracted from the semiconductor layer through the through hole 17. The angle can be increased, the proportion of reflected light can be reduced, and more light entering the through hole 17 from the semiconductor layer can be extracted to the outside.

The critical angle θ _r when the through hole 17 is filled with a resin material is about 36 ° from the above formula. Therefore, the minimum diameter of the through hole 17 from which light can be extracted efficiently is 2 μm from the light emitting layer 13 to the interface between the substrate 10 and the buffer layer 11 because D _h = 2 · D _s · tan θ _r. In this case, the minimum diameter of the through hole 17 can be determined to be about 2.9 μm. If the diameter of the through hole 17 is equal to or larger than the minimum diameter, light can be effectively extracted outside through the through hole 17.

The translucent member 18 made of such a resin material does not necessarily need to be completely filled in the through-hole 17, and obtains the same effect even if it is formed so as to cover the inner surface of the through-hole 17. be able to. Further, as another material of the translucent member 18, SiO ₂ can be used.

  Furthermore, the configuration of the third embodiment of the present invention is shown in FIG. In the third embodiment, as in the first embodiment, the gallium nitride compound semiconductor 100 is formed on the substrate 10 via the buffer layer 11 by the MOCVD method.

  In the third embodiment, preferably, the through-hole 17 is provided with a reflective member 19 that reflects light emitted from the light emitting layer 13 on the side surface or the upper surface side end of the substrate 10. When the light emitted from the light emitting layer 13 is taken out to the surface of the semiconductor layer opposite to the substrate 10, if there is a reflective member 19 at the end of the through hole 17 on the upper surface side of the substrate 10, The light can be reflected and the light extraction efficiency can be increased. In addition, when the reflective member 19 is provided on the side surface of the through hole 17, when light is extracted from the semiconductor layer to the substrate 10 side, the light is efficiently reflected on the side surface of the through hole 17 to the substrate 10 side. The light extraction efficiency can be increased.

  Further, as shown in FIG. 6, a reflective member 19 may be provided on the upper surface side end portion and the side surface of the substrate 10 of the through hole 17. In this case, light can be efficiently extracted to the surface of the semiconductor layer opposite to the substrate 10, and when the lower surface of the substrate 10 is used as an electrode, current can be efficiently supplied to the semiconductor layer with low resistance. High luminous efficiency can be obtained.

  The material of the reflective member 19 is preferably made of at least one of aluminum (Al), silver (Ag), rhodium (Rh), and palladium (Pd). Since these materials have a high reflectivity from the ultraviolet light region to the visible light region, the light emitted from the light emitting layer 13 to the substrate 10 side can be efficiently reflected by the reflective member 19, so that the external quantum efficiency Can be increased. Moreover, the reflective member 19 may be comprised from the some laminated body. For example, the above-described reflective material layer may be stacked after a light-transmitting material layer or a very thin metal thin layer is stacked on the first layer.

  The reflective member 19 is formed by opening a through hole 17 in the substrate 10 by a method such as wet etching, and then using a resistance heating vapor deposition method, an electron beam vapor deposition method, a sputtering method, an electroplating method, an electroless plating method, or the like. Thus, it can be formed by stacking or vapor deposition.

  The thickness of the reflective member 19 is preferably 10 nm or more because light is transmitted when it is extremely thin.

  In the configuration of FIG. 6, when a conductive substrate is used as the substrate 10, the substrate 10 can be the n-type electrode 15, and in that case, it is not necessary to expose a part of the n-type layer 12.

Further, in the substrate 10 made of an insulating material such as sapphire (Al ₂ O ₃ ), a current can be passed through the reflective member 19 such as a metal formed in the through hole 17 in the same manner. An n-type electrode 15 may be formed.

In the light emitting element such as an LED using the gallium nitride compound semiconductor (In _x Al _y Ga _1-xy N; 0 ≦ x, y ≦ 1, x + y ≦ 1) Improve the light emission efficiency of the light emitting element, in particular, the light extraction efficiency for extracting the light emitted from the active layer 13 to the outside of the semiconductor layer, without performing complicated steps such as removing the substrate 10 and causing damage to the semiconductor layer. Can be made.

  In addition, this invention is not limited to said embodiment and Example, A various change can be given in the range which does not deviate from the summary of this invention.

It is sectional drawing of the light emitting element using the conventional gallium nitride type compound semiconductor. It is sectional drawing of the light emitting element in the 1st Embodiment of this invention. (A), (b) is sectional drawing which shows the through-hole in the 1st Embodiment of this invention, respectively. (A)-(f) is a top view of the through-hole in the 1st Embodiment of this invention, respectively. It is sectional drawing of the light emitting element in the 2nd Embodiment of this invention. It is sectional drawing of the light emitting element in the 3rd Embodiment of this invention.

Explanation of symbols

10: substrate 11: buffer layer 12: n-type gallium nitride compound semiconductor layer 13: light emitting layer 14: p-type gallium nitride compound semiconductor layer 15, 16: electrode 17: through hole 18: translucent member 19: reflective Element

Claims (6)

A semiconductor layer including an n-type gallium nitride compound semiconductor layer, a p-type gallium nitride compound semiconductor layer, and a light emitting layer made of a gallium nitride compound semiconductor is formed on the upper surface of the sapphire substrate, and the n-type gallium nitride is formed. The n-type electrode connected to the compound compound semiconductor layer and the p-type electrode connected to the p-type gallium nitride compound semiconductor layer are formed in the same main surface direction of the semiconductor layer and emit light in the light emitting layer In the light emitting device having a flip chip structure in which light is extracted from the substrate side, the substrate has a plurality of through holes that penetrate the upper and lower surfaces and reach the semiconductor layer, and the diameter D _{h of the} through holes is the refractive index of the semiconductor layer n ₁ and the refractive index of the through-hole and n _2, the distance from the light-emitting layer to the substrate is taken as _{D s, D h ≧ 2 ×} D s × tanθ _{(However, θ r = arcsin (n 1} / n 2)) light emitting element characterized der Rukoto.   2. The light emitting device according to claim 1, wherein the semiconductor layer is roughened only at a portion facing the through hole in a surface in contact with an upper surface of the substrate.   3. The light emitting device according to claim 1, wherein the through hole is filled with a light transmissive member having a refractive index between the refractive index of air and the refractive index of the gallium nitride compound semiconductor. .   The light-emitting element according to claim 1, wherein the through-hole is provided with a reflective member on a side surface for reflecting light emitted from the light-emitting layer.   5. The light-emitting element according to claim 1, wherein the opening of the through hole has an aperture ratio that is a ratio of an area of the upper and lower surfaces of the substrate of 50% to 95%.   The light-emitting element according to claim 1, wherein a diameter of the through hole gradually decreases toward an interface between the substrate and the semiconductor layer.

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